In case you have got your iPhone 4S and enjoyed with Siri, you might have known that Siri has a female’s voice. In case you’ve asked Siri some sexually questions such as “What are you wearing?”, you’ll get a female-related answer.

It’s much easier to find a female voice that everyone likes than a male voice that everyone likes,” said Stanford University Professor Clifford Nass, author of “The Man Who Lied to His Laptop: What Machines Teach Us About Human Relationships.” “It’s a well-established phenomenon that the human brain is developed to like female voices.”

Research suggests this preference starts as early as the womb, Nass said. He cites a study in which fetuses were found to react to the sound of their mother’s voice but not to other female voices. The fetuses showed no distinct reaction to their father’s voice, however.

Also Apple commented about Siri’s female voice:

An Apple spokeswoman declined to comment on why the company gave Siri a female voice in the U.S. Nor would she say why Siri speaks like a man in the UK, where iPhone 4S owners have swarmed online forums to request a female voice instead. “Eww!! Hope UK gets female voice soon,” wrote one commenter. “I don’t think anyone in the US cares about male voice option.